You cannot spot reduce an area on the body. With that note, you have to perform high intensity interval training for about 20-30 minutes, and watch what you eat. Having a clean diet is the key. I always say 80% diet and 20% working out. So they both complement each other and this is how you will see results to burn the fat away. I do like to do side planks with my clients because it does help strengthen the core, and help support the lower back. Stay away from weighted side bends. I see too many people performing this exercise. It creates shear on the sacrum of the spine, which will create wear and tear, so avoid them at all costs.